Let us consider a classical "White to move and mate in 2 moves" problem.
The requirement in quotes above is called a Stipulation.
The formal sequence of the moves in a correct two move composition is:

* White makes the first move
* Black defends by making his first move
* White makes his second move and mates black

There are, however, specific terms used for each of these moves.

(1) White's first move is called:

- A Key move or simply key, if it is the only correct move solve the problem.
- A Cook , if it is another move that also solves the problem. The problem itself is then called cooked and considered faulty and worthless.
- A Try move or simply try, if it 'almost' solves the problem. More specifically there is only one black first move that refutes that white try.There can be several tries in a problem and they are often very integral part of the composition. Some composers positively excel in snaring the solvers in tries.
- If the first white move is neither key,cook nor try, then it is - well- just a move, which black can refute at least in two ways.

(2) Black's first move is called:

- A refutation, if there is no mate with white's second move.
- A variation, if there is a new, different mate with white's second move. Obviously a correct problem will have at least one variation. Normally there are several variations associated with different mates. As with tries, the set of variations may well reveal the artistic content of the composition and it is assumed that a solver will see them all. Else he does not know, if he has correctly solved the problem - of course. If the key is correct, black's first move is always part of the variation set. After a try or other faulty first move the first black move may be a refutation or just faulty defence allowing mate by mistake.

(3) White's second (mating) move is called:

- A mate (obviously). But there can be several mates. In fact it is the number of different mates that separates the number of variations.The mate that defeats most of the black's defences is considered the principal solution (or main line) and other mates are end nodes of variations.
- A dual, in case that there are more than one mating moves against a given black defence. A dual is not as bad as a cook, but is generally frowned upon. Still sometimes a bit of duality may be necessary for 'greater good' in expressing a complex idea in a composition.

There's a lot more to say, but this perhaps gives a basic idea of some terms regarding moves and their names in direct two-move mate problems._________________There are only three kinds of chessplayers - those who can count and those who cannot....